The existing day-and-night monitoring cameras are commonly equipped with a light sensor, so as to determine whether to perform an IR-cut (Infrared-cut) filter switching operation or to turn on IR LEDs (Light Emitting Diodes) according to the environment brightness sensed by the light sensor. However, the drawback of the existing day-and-night monitoring cameras is that the image always has an overexposure issue or an underexposure issue when the amount of light passing through the lens of the monitoring camera alters with a modulation of a focal length of the lens. Thus, the light sensor of the monitoring camera cannot operate properly.
Although the industry in this field has developed a technology capable of determining whether to perform the IR-cut filter switching operation or to turn on the IR LEDs in accordance with the image brightness, this technology still has a flaw that the image brightness cannot be further utilized to determine whether to perform the IR-cut filter switching operation or to turn on the IR LEDs when the IR LEDs have been turned on.